just looked jerseys have a coefficency of 3.3 percent and don’t go higher than 6 percent
inbreeding causes less milk production after that
that’s quite low inbreeding
khan jihad had 9.51 and he only had 3x3 common relative grandparent each side litter brother sister with some import blood a bit further back
imagine what brother sister then a pup back to farther would be even the kc wouldn’t have that ?